# AS chemistry - calculating enthalpy changesWatch

#1
When 25cm^3 of 0.5moldm^3 magnesium chloride solution was added to 25cm^3 carbonate solution, the temperature fell by 0.75 degrees C and a precipitate of magnesium carbonate was formed. Write a full equation for the reaction that occurs and calculate the enthalpy change for the reaction in kJmol-1

Any help would be great!
0
4 years ago
#2
(Original post by Chloe_Louise1)
When 25cm^3 of 0.5moldm^3 magnesium chloride solution was added to 25cm^3 carbonate solution, the temperature fell by 0.75 degrees C and a precipitate of magnesium carbonate was formed. Write a full equation for the reaction that occurs and calculate the enthalpy change for the reaction in kJmol-1

Any help would be great!
What've you done so far? You'll want to use the formula Q=mcT (where T is change in temperature).
0
#3
(Original post by Chlorophile)
What've you done so far? You'll want to use the formula Q=mcT (where T is change in temperature).
I got q = 50 x 4.18 x 0.75 = 156.75 J

no. moles MgCl2 = 0.5x25/1000 = 0.0125

0.0125 moles MgCl2 = 156.75J heat

So 1 mole MgCl2 = 156.75/0.0125 = 12.54 kJ mol -1 = enthalpy change
0
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